1、BS EN 14358:2016Timber structures Calculation and verification ofcharacteristic valuesBSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06BS EN 14358:2016 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN 14358:2016.It supersedes BS EN
2、 14358:2006 which is withdrawn.The UK participation in its preparation was entrusted to TechnicalCommittee B/518, Structural timber.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovision
3、s of a contract. Users are responsible for its correctapplication. The British Standards Institution 2016.Published by BSI Standards Limited 2016ISBN 978 0 580 83527 8ICS 79.040; 91.080.20Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was publis
4、hed under the authority of theStandards Policy and Strategy Committee on 30 June 2016.Amendments/corrigenda issued since publicationDate T e x t a f f e c t e dBS EN 14358:2016EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 14358 June 2016 ICS 79.040; 91.080.20 Supersedes EN 14358:2006English V
5、ersion Timber structures - Calculation and verification of characteristic values Structures en bois - Dtermination et vrification des valeurs caractristiques Holzbauwerke - Berechnung und Kontrolle charakteristischer Werte This European Standard was approved by CEN on 23 January 2016. CEN members ar
6、e bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to
7、the CEN-CENELEC Management Centre or to any CEN member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Ce
8、ntre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithua
9、nia, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG CEN-CENELEC Management Centre: Avenue Marnix 17, B-1
10、000 Brussels 2016 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 14358:2016 EBS EN 14358:2016EN 14358:2016 (E) 2 Contents Page European foreword . 3 1 Scope 4 2 Symbols . 4 3 Calculation of characteristic properties from test resu
11、lts in the frame of initial type testing 5 3.1 General 5 3.2 Calculation of 5 and 95 percentiles values. 5 3.2.1 General 5 3.2.2 Parametric calculation 5 3.2.3 Non parametric calculation . 7 3.3 Calculation of characteristic mean values . 7 4 Calculation of characteristic properties from test result
12、s in the frame of internal factory production control 9 4.1 General 9 4.2 Calculation of characteristic strength, density or resistance properties (5-percentile) . 9 4.3 Calculation of characteristic stiffness properties (mean values) . 11 5 Acceptance procedure for verification of a lot 12 5.1 Gene
13、ral . 12 5.2 Verification of mean values (e.g. mean modulus of elasticity) 12 5.2.1 Method keeping the consumers risk at 10 % 12 5.2.2 Alternative method limiting the sample size for large COVs 13 5.3 Verification of 5-percentile values (e.g. characteristic strength) . 13 5.3.1 Method with consumers
14、 risk equal to 10 % 13 5.3.2 Alternative method limiting the sample size for large COVs 14 Bibliography . 15 BS EN 14358:2016EN 14358:2016 (E) 3 European foreword This document (EN 14358:2016) has been prepared by Technical Committee CEN/TC 124 “Timber structures”, the secretariat of which is held b
15、y AFNOR. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by December 2016, and conflicting national standards shall be withdrawn at the latest by December 2016. Attention is drawn to the possibility
16、that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. This document supersedes EN 14358:2006. This document is based on Annex D of EN 1990:2002, Eurocode Basis of structural desi
17、gn. Compared to EN 14358:2006, the following modifications have been made: integration of normal distributions, and non parametric estimation; proposals for simplified equations to evaluate correction factors; estimation of mean values; acceptance procedure for verification of a lot (taken from EN 3
18、84: 2010). According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
19、France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. BS EN 14358:2016EN 14358:2016 (E) 4 1 Scope This standard gives statistical
20、methods for the determination of characteristic values from test results on a sample drawn from a clearly defined reference population of e.g. solid wood, fasteners, connectors and wood-based products. The characteristic value is an estimate of the property of the reference population and can be bas
21、ed on a 5-percentile value of strength, resistance or density as well as on a mean value for stiffness. Parametric methods are given for the determination of lower and upper 5-percentiles. The upper 5-percentile is the 95-percentile. This standard is suitable for use with any structural product in t
22、he frame of type testing as well as factory production control. Sampling is not covered by this document, but reference is made to the relevant product standards. This standard also provides the acceptance procedure for verification of a lot. Depending on the product, characteristic values determine
23、d in accordance with this standard may be used directly or may need additional adjustments specified in the relevant product standards. Note: For example, in the case of solid timber, specific adjustment factors for calculation of characteristic values are given in EN 384. 2 Symbols s()kn Factor use
24、d to calculate characteristic properties for initial type testing (see Tables 1 and 2) ()kn Factor used to calculate characteristic properties for factory production control (see Tables 3 and 4) miIndividual test value i of stochastic variable m mk5-percentile value of stochastic variable m meanm Po
25、pulation mean value of stochastic variable m n Number of test values sy Standard deviation uxx-percentile in the standardised normal distribution y Sample mean value y = m for normally distributed variable y = ln m for logarithmically normally distributed variable 5.0y Sample 5-percentile from the t
26、est data Confidence level (%) BS EN 14358:2016EN 14358:2016 (E) 5 3 Calculation of characteristic properties from test results in the frame of initial type testing 3.1 General The characteristic value of a material parameter or a resistance shall be determined at a confidence level of = 75 %, where
27、the confidence level is defined as the probability of which the characteristic value is greater than the estimator on the characteristic value. NOTE The confidence level = 75 % corresponds to the value recommended in EN 1990. 3.2 Calculation of 5 and 95 percentiles values 3.2.1 General a) The charac
28、teristic value km for a material strength parameter or a resistance m modelled as a stochastic variable is defined as the p -percentile in the distribution function for m , corresponding to an assumed infinitely large test series; b) p = 5 % shall be assumed. 3.2.2 Parametric calculation a) The para
29、metric approach shall not be used on test data not fitting the assumed distribution. In that case, a non-parametric method should be used; b) It is assumed that n test values are available and that these may be assumed to originate from a statistically homogeneous population. The test values, which
30、are assumed to be logarithmically normally distributed or normally distributed and independent, are denoted 12, ,nmm m. The n test values constitute the sample; c) Strength parameters should be assumed as logarithmically normally distributed unless analysis of the data shows that a normal distributi
31、on is more appropriate. Density shall be assumed as normally distributed; NOTE Some product standards define the statistical distribution to be used. d) The mean value y and the standard deviation syshall be determined as: logarithmically normally distributed normally distributed =11lnniiymn(1) =11n
32、iiymn(2) =211(ln )max10,05niyimysn(3) =211()max10,05niyimysny(4) The sample coefficient of variation shall not be taken as less than 0,05. For logarithmically normally distributed test values, the standard deviation syshall not be less than( )+2ln 1 0,05 0,05 . BS EN 14358:2016EN 14358:2016 (E) 6 Fo
33、r normally distributed test values, the standard deviation syshall not be less than 0,05 y . e) The characteristic value of the sample shall be determined as follows: percentile logarithmically normally distributed normally distributed 5-percentile ( )= k syexp ( )m y k ns (5) = k sy()m y k ns (6) 9
34、5-percentile ( )= +k syexp ( )m y k ns (7) = +k sy()m y k ns (8) f) s()kn shall be taken as: =s()()knknn(9) where ()kn is the -percentile in a non-central t-distribution with n 1 degrees of freedom and the non-centrality parameter = 1pun. whereby u1-pis the (1 p)-percentile of the standardised norma
35、l distribution function. The following simplified expression may be used to evaluate s()kn +=s6,5 6()3,7 3nknn(10) Some values of s()kn calculated according to Formula (9) are given in Table 1. Table 1 ( )skn values for strength properties for p = 5 % and = 75 % Number of test specimens Factor n s()
36、kn 3 3,15 5 2,46 10 2,10 15 1,99 20 1,93 30 1,87 50 1,81 100 1,76 500 1,69 1,64 For other numbers of test specimens, one should take the value corresponding to the next smallest value of n listed in this table. BS EN 14358:2016EN 14358:2016 (E) 7 3.2.3 Non parametric calculation a) Non parametric ca
37、lculation shall not be applied if the sample size is less than =40n ; b) The 5-percentile of the test data shall be evaluated by ranking the test data and determining the 5-percentile of the ranked data; To rank the data, any p-percentile value fpshall be linearly interpolated from the empirical cum
38、ulative frequency distribution of the test data ranked in ascending order. The i-th data point in the empirical cumulative frequency distribution of the test data (ranked in ascending order) shall be taken to be the percentile (p) given by the following equation: =ipn(11) where n sample size i i-th
39、data point ranked in ascending order c) The 5-percent lower tolerance limit with 75 % confidence shall be evaluated from Formula (12): =nVkymk75.0,5.05.01 (12) where n is the number of test values km is the 5-percent lower tolerance limit with 75 % confidence 5.0y is the 5-percentile from the test d
40、ata V is the coefficient of variation of the test data found by dividing the standard deviation of the test data by the average of the test data k0.5,0.75 is a multiplier to give the 5-percent lower tolerance limit with 75 % confidence: 1,728,01749,075.0,5.0+=nnk (13) 3.3 Calculation of characterist
41、ic mean values a) The characteristic value meanm for a material stiffness m modelled as a stochastic variable is defined as the mean value in the distribution function for m , corresponding to an assumed infinitely large test series; b) It is assumed that n test values are available and that these m
42、ay be assumed to originate from a homogeneous population. The test values, which are assumed to be normally distributed and independent, are denoted 12 n, ,mm m. The n test values constitute the sample; BS EN 14358:2016EN 14358:2016 (E) 8 c) The sample mean value y and the sample standard deviation
43、syfor the stochastic variable y = m shall be determined as: = i11niymn(14) =2iy11()max10,05nimysny(15) d) For stiffness properties, the characteristic mean value shall be taken as the sample mean value y as given in Formula (14); e) When it is required to make use of confidence intervals, the charac
44、teristic mean value mmeanshall be determined as. = mean s y()m y k ns (16) where =,n 1s()tknn(17) ,n 1t is the percentile in a central t-distribution with n-1 degrees of freedom. Some values of s()kn are given in Table 2. For other numbers of test specimens, one should either interpolate or take the
45、 safer value for s()kn, i.e. the one which is larger. The following simplified equation may also be used to evaluate. =s0,530,78()knn(18) BS EN 14358:2016EN 14358:2016 (E) 9 Table 2 ( )skn values for stiffness properties Number of test specimens Factor n ()skn 3 0,471 5 0,331 10 0,222 15 0,179 20 0,
46、154 30 0,125 50 0,096 100 0,068 500 0,030 0,000 4 Calculation of characteristic properties from test results in the frame of internal factory production control 4.1 General If a variable control method is applied to control the material parameters or resistance, such control method shall be composed
47、 with a significance level of = 75 %, where the significance level is defined as the probability of not accepting a batch having the required characteristic value. NOTE The significance level = 75 % corresponds to the value required in Clause 3. 4.2 Calculation of characteristic strength, density or
48、 resistance properties (5-percentile) a) It is assumed that n test values are available and that these may be assumed to be derived from a homogeneous population described by the stochastic variable m. The test values which are assumed to be logarithmically normally distributed or normally distribut
49、ed, are denoted 12 n, ,mm m. The n test values constitute the sample; b) Strength parameters shall be assumed as logarithmically normally distributed. Density shall be assumed as normally distributed; c) The mean value y and the standard deviation syshall be determined as: logarithmically normally distributed normally distributed = i11lnniymn(19) = i11niymn(20) BS EN 14358:2016EN 14358:2016 (E) 10 = 2yi11(ln )1nis myn(21) = 2yi11()1nis myn(22) d) The control
